1. Field of the Invention
This invention relates to an optical disk recording method and an apparatus for use in such method, in which a laser power (intensity of a recording laser beam) during a pit formation is controllable to an optimal value where a favorable recording condition is achieved.
2. Prior Art
In recording on a write-once-read-many optical disk such as a CD-R or a DVD-R, test recording is performed with various settings of a laser power before actual recording, recorded data are reproduced after the test recording to obtain a laser power where an optimal recording condition is achievable (for example, where an asymmetry value of a target reproduction signal is achievable), and then a laser power is set to the optimal value to perform the actual recording. Even if the optimal recording condition is achieved at the beginning of the recording, however, it sometimes becomes hard to achieve the optimal recording condition in the initial laser power as the recording proceeds due to a change in the disk condition such as a disk warp or a change in a film thickness of a recording layer (a pigment film formed by a spin coat method sometimes has a different film thickness between the inner circumferential side and the outer circumferential side of the disk). Therefore, there have conventionally been suggested methods of controlling a laser power in real time to a value where an optimal recording condition is achievable by detecting the recording condition while recording is performed. One of those is a method of controlling a laser power on the basis of a returning light receiving signal of a main beam for recording.
In the method of controlling the laser power on the basis of the returning light receiving signal of the main beam, there is a need for sampling the returning light receiving signal of the main beam during a period in which the returning light receiving signal of the main beam shows a stable level. High-speed recording, however, causes the period in which the returning light receiving signal of the main beam shows the stable level to be short, thereby making it hard to control the sampling timing of the returning light receiving signal of the main beam.